In the International Study of Kidney Disease in Children 24 participating clinics in 12 countries throughout the world are conducting clinical surveys and therapeutic trials on major kidney diseases in children. Trials in progress include: 1. the effect of cyclophosphamide in patients with a. focal segmental sclerosis and b. anaphylactoid purpura; 2. the effect of prednisone in patients with a. minimal change nephrotic syndrome and b. membranoproliferative glomerulonephritis; 3. imuran in patients with severe lupus nephritis. Clinical surveys are being conducted on the natural history of patients with 1. the nephrotic syndrome; 2. recurrent hematuria; 3. familial nephritis; and 4. membranous nephropathy. New controlled trials are being begun on a. the effect of prednisone, azothioprine, cyclophosphamide versus these agents plus dipyridamol and heparin in patients with severe rapidly progressive glomerulonephritis and b. different forms of prednisone in patients with minimal change nephrotic syndrome.